On OKX, i was able to use derivative trading, and able to withdraw to certain amount. I left the exchange for like a month or two. When I go back to the exchange, i deposited some amount of bitcoin. I converted it to USDT. A time came when I wanted to move the USDT to another address, i was asked to verified my mobile number. I was unable to withdraw until I was able to verify my mobile number. I wanted to create a thread about this some months ago when it happened, but i just think it is not necessary because it is still a centralized exchange.
This happens quite often if you use the OKX exchange strictly for depositing / withdrawing coins with small amounts, as an exchanger. The exchange does not like this and therefore may ask people to verify their phone number. Any centralized service is a risk, but have not yet created a full-fledged DEX that would completely replace exchanges like OKX, so their use will still be relevant. But now it is already such a time that most crypto users are not at all embarrassed by KYC.